Normally, when I make pico de gallo, I use tomato, red onion, and jalapeño. This week, the garden is spewing forth dozens of cucumbers, so I'm throwing those in as well.
There really isn't a recipe for pico... you just throw whatever you want in there. I'll list what I used, but I also won't give amounts. If you don't groove on onion, use less. If you don't like cucumbers, don't use them. Do whatever makes you happy!
Cucumber Pico de Gallo
6 lemon cucumbers, diced (I don't seed mine)
6 roma tomatoes, diced (I squish out the jelly stuff so the mixture doesn't get too soupy)
1 small red onion, minced
1 small jalapeño, minced
Fresh lime juice
Red wine vinegar
Mix everything up and let it sit at least 30 minutes before you attack it. If you have the willpower... I never do!